3,2

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 171.

E. M. Palmer and R. W. Robinson, Enumeration under two representations of the wreath product, Acta Math., 131 (1973), 123-143.

Cf. A003224, A003223.

Sequence in context: A032078 A067210 A018654 this_sequence A007663 A018695 A156336

Adjacent sequences: A003222 A003223 A003224 this_sequence A003226 A003227 A003228

nonn,easy,more

N. J. A. Sloane (njas(AT)research.att.com).